Modern computer systems have evolved so that different circuitry components may be connected to a common bus which allows information to be passed back and forth as electrical signals between the components. The design of the bus, and the format and meaning assigned to bus signals is set by a bus protocol, which may be formalized as an industry standard adopted by manufacturers. One such industry standard protocol is the Small Computer System Interface (SCSI) protocol that provides for a nine bit parallel bus which includes one parity bit, and nine control lines, which combined are referred to as a "SCSI bus" and which has a total of eighteen lines. That standard is a draft standard proposed by the ANSI X3T9.2 task group.
A known method of connecting to a SCSI bus is to connect a microprocessor to SCSI interfacing circuitry, which typically consists of discrete devices, external drivers, and a SCSI interface integrated circuit chip. Typically, the microprocessor performs various functions to control the interfacing circuitry in accordance with the SCSI protocol.
A problem encountered with prior SCSI interfacing circuitry is the limited rate at which large amounts of data may be transferred from point to point through a SCSI bus.
Another problem encountered with prior SCSI interfacing circuitry is the large amount of time and instruction storage required by the microprocessor to perform various SCSI protocol functions in controlling the SCSI interfacing circuitry.